This application claims benefit of U.S. Provisional Application No. 62/047,344, filed on Sep. 9, 2014 and which application is incorporated herein by reference. A claim of priority is made.
Solid drug delivery implants are utilized to provide sustained release of an active agent or drug over a period of days, weeks, months, or years as an attractive alternative to more conventional dosage forms, such as oral or parenteral dosages. A few examples of such products include subcutaneous “rod” implants, intrauterine devices, and intravaginal rings (IVRs). In order to provide consistent and constant drug release rates a preferred approach is to embed the drug within a polymer matrix of material and encapsulate it within a polymer membrane or sheath to provide a barrier for controlled drug diffusion and release. Typically the drug is incorporated into the polymer by a hot melt extrusion process to produce drug-doped pellets. These pellets are then extruded to form the drug-filled core, and a rate-controlling sheath is coextruded over the drug-filled core. Drug-filled cores, and appurtenant sheaths, are extruded in lengths, typically with circular cross-sections. When continuous implant shapes are desired, the sheathed cores must be cut to length and the ends must be welded together.
In cases where a very thin (<0.5 mm, frequently 0.10 mm or less) sheath thicknesses are advantageous or required, control of thickness during extrusion can be problematic and required expensive in-line process control and equipment. The extrusion process also subjects the drug to significant thermal loads which can cause a range of deleterious effects, including chemical degradation of the drug and/or matrix and sheath components, crystallization within the polymer matrix. Further, the process often demands relatively large amounts of material resulting in wasted active ingredients and polymer material. Additionally, coextrusion equipment and subsequent process steps (e.g. welding into rings) can also be expensive and engender process inefficiency.